King penguins stand at about one metre tall. While adults will set to sea for days at a time foraging for food, the species does not migrate.

The reason behind the colony's decimation on Ile aux Cochons remains a mystery.

"It is completely unexpected, and particularly significant since this colony represented nearly one-third of the king penguins in the world," study lead author Henri Weimerskirch, an ecologist at the Centre for Biological Studies in Chize, France, told AFP news agency on Monday.

Why the colony on Ile aux Cochons has been so decimated remains a mystery [File: Auscape/UIG via Getty Images]

Climate change

In 1997, a particularly strong El Nino weather event warmed the southern Indian Ocean, temporarily pushing the fish and squid on which king penguins depend south.

"This resulted in population decline and poor breeding success" for all the king penguin colonies in the region, Weimerskirch said.

El Nino's are cyclical events that occur every two to seven years. But they can be amplified by global warming, which itself produces many of the same results, albeit on a longer timescale.

Migration is not an option because there are no other suitable islands within striking range. Other factors may be contributing to the decline of the Ile aux Cochons colony, including overcrowding.

A study published last February estimated that 70 percent of the king penguin species would either have to relocate or would vanish before the end of the century, this based on climate change models predicted.

Populations of most of 18 types of penguins are decreasing, according to a Red List run by conservation experts.

Populations of most of 18 types of penguins are decreasing [File: Wolfgang Kaehler/ via Getty Images]

One egg at a time

"The larger the population, the fiercer the competition between individuals," France's National Centre for Scientific Research, which funded the study, said in a statement.

"The repercussions of lack of food are thus amplified and can trigger an unprecedented rapid and drastic drop in numbers."

But this so-called "density-dependent effect" can also be made worse by climate change, the study said.

Another possible culprit is avian cholera, which has affected seabirds on nearby Marion and Amsterdam Islands, including some king penguins.

It is also possible that invasive species such as rats, mice or cats have found their way onto the island.

King penguins are the second-largest penguin species after the emperor.